Japanese Laid-Open Patent Publication No. 2000-298733 (hereinafter referred to as Patent Document 1), for example, discloses a game device in which the trace of the movement of an object is displayed as the object is moved around in a virtual game world. With the game device, the trace (path) of the movement of the object in the virtual game space is rendered with polygons, and the color of each portion of the trace is lightened gradually with time until that portion disappears, whereby portions of the trace that are closer to the rear end thereof are lighter in color.
However, the game device disclosed in Patent Document 1 requires more polygons to be rendered for displaying longer traces in the virtual game space, thus needing to reserve a memory space for the polygons. Therefore, the maximum length of the trace to be displayed is limited by the processing speed of the game device and the allotted memory size.
Therefore, a feature of certain exemplary embodiments is to provide a storage medium storing a game program and a game device for displaying a trace of the movement of an object with no limitation on the maximum length of the trace to be displayed.
Certain exemplary embodiments described herein have the following aspects to attain the feature mentioned above. Note that parenthetic expressions in the following section (reference numerals, step numbers, etc.) are merely to indicate the correlation between what is described in the following section and what is described in the detailed description set out further below in the present specification, and are in no way intended to restrict the scope of the certain exemplary embodiments described herein.
A first aspect of certain exemplary embodiments is directed to a storage medium storing a game program to be executed by a computer (30) of a game device (5) for displaying, on a display device (2), an object (PC) moved around in a virtual game world. The game program instructs the computer to perform an object position calculation step (the CPU 30 performing step 15; hereinafter only the step numbers will be shown), a trace shape information updating step (S46), a ground texture producing step (S51), a game field rendering step (S52), an object placement step (S15), and a display control step (S53, S13). The object position calculation step is a step of calculating a position (Db) of the object in the virtual game world. The trace shape information updating step is a step of updating trace shape information (Tsa) representing a shape of a trace (M) along which the object has moved across a game field in the virtual game world based on a change in the calculated position, and storing the updated trace shape information in a memory (33). The ground texture producing step is a step of producing a ground texture (Tc) by blending together an image (Tt) of the game field in the virtual game world with the trace and that (Tg) without the trace based on the trace shape information. The game field rendering step is a step of rendering the game field in the virtual game world by using the ground texture. The object placement step is a step of placing the object at the calculated position. The display control step is a step of displaying the virtual game world in which the object has been placed on the display device.
In a second aspect based on the first aspect, the object position calculation step, the trace shape information updating step, the ground texture producing step, the game field rendering step, and the display control step are repeated by the computer on a predetermined processing cycle.
In a third aspect based on the first aspect, the trace shape information indicates a blending ratio at which the image of the game field with the trace is blended with that without the trace.
In a fourth aspect based on the third aspect, in the trace shape information updating step, the trace shape information is updated while the blending ratio at which the image of the game field with the trace is blended is lowered for portions of the trace that have already been rendered and displayed on the display device.
In a fifth aspect based on the first aspect, the trace shape information indicates an area where the image of the game field with the trace is blended with that without the trace.
In a sixth aspect based on the fifth aspect, the trace shape information further indicates a blending ratio at which the image of the game field with the trace is blended in the area.
In a seventh aspect based on the sixth aspect, in the trace shape information updating step, the trace shape information is updated while the blending ratio at which the image of the game field with the trace is blended is lowered for portions of the trace that have already been rendered and displayed on the display device.
In an eighth aspect based on the first aspect, the trace shape information is image data such that an area of the game field where the trace is present is represented in a first color (black) and an area of the game field where the trace is absent is represented in a second color (white) different from the first color, and the blending ratio at which the image of the game field with the trace is blended with that without the trace is represented in terms of a strength of the first color.
A ninth aspect of certain exemplary embodiments is directed to a game device for displaying an object moved around in a virtual game world on a display device. The game device includes the object position calculation means, the trace shape information updating means, the ground texture producing means, the game field rendering means, the object placement means, and the display control means. The object position calculation means is means for calculating a position of the object in the virtual game world. The trace shape information updating means is means for updating trace shape information representing a shape of a trace along which the object has moved across a game field in the virtual game world based on a change in the calculated position, and storing the updated trace shape information in the storage means. The ground texture producing means is means for producing a ground texture by blending together an image of the game field in the virtual game world with the trace and that without the trace based on the trace shape information. The game field rendering means is means for rendering the game field in the virtual game world by using the ground texture. The object placement means is means for placing the object at the calculated position. The display control means is means for displaying the virtual game world in which the object has been placed on the display device.
In a tenth aspect based on the ninth aspect, the processes performed by the object position calculation means, the trace shape information updating means, the ground texture producing means, the game field rendering means, and the display control means are repeated on a predetermined processing cycle.
In an eleventh aspect based on the ninth aspect, the trace shape information indicates a blending ratio at which the image of the game field with the trace is blended with that without the trace.
In a twelfth aspect based on the eleventh aspect, the trace shape information updating means updates the trace shape information while the blending ratio at which the image of the game field with the trace is blended is lowered for portions of the trace that have already been rendered and displayed on the display device.
In a thirteenth aspect based on the ninth aspect, the trace shape information indicates an area where the image of the game field with the trace is blended with that without the trace.
In a fourteenth aspect based on the ninth aspect, the trace shape information further indicates a blending ratio at which the image of the game field with the trace is blended in the area.
In a fifteenth aspect based on the fourteenth aspect, the trace shape information updating means updates the trace shape information while the blending ratio at which the image of the game field with the trace is blended is lowered for portions of the trace that have already been rendered and displayed on the display device.
In a sixteenth aspect based on the ninth aspect, the trace shape information is image data such that an area of the game field where the trace is present is represented in a first color and an area of the game field where the trace is absent is represented in a second color different from the first color, and the blending ratio at which the image of the game field with the trace is blended with that without the trace is represented in terms of a strength of the first color.
According to the first aspect, before the virtual game world is rendered, only the trace is rendered, and the rendered trace is made into a texture, which is displayed while being blended with the ground. Therefore, the processing speed and the memory cost required for rendering the trace can be kept constant, irrespective of the size of the trace to be rendered. Moreover, the ground texture is produced by blending together two different images of the game field, whereby it is possible to produce the ground that fits the game field.
According to the second aspect, the trace rendering process is repeated, whereby the trace can be updated and appropriately rendered as the object moves around.
According to the third aspect, the ratio at which the image of the game field with the trace is blended can be controlled, whereby the shade of the trace can be expressed on the game field.
According to the fifth aspect, it is possible, using the trace shape information, to render a trace according to the path along which the object has passed.
According to the sixth aspect, it is possible, using the trace shape information, to render a trace according to the path along which the object has passed, while expressing the shade thereof on the game field.
According to the fourth or seventh aspect, the color of each portion of the trace is lightened gradually with time until that portion disappears.
According to the eighth aspect, the trace shape information can be realized as image data such that the trace shape is displayed in a first color (e.g., black) and the area other than the trace is displayed in a second color (e.g., white), and the shade of the trace is represented in terms of the strength of the first color.
With the game device of certain exemplary embodiments, effects similar to those of the storage medium storing a game program can be obtained.
These and other objects, features, aspects and advantages of the certain exemplary embodiments will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.